Shear through or nibble away at sheet metal that too hard to cut with tin snips. These sheet metal hand nibblers can cut through metal up to 1/8 in thick. These hand nibblers use more of a shearing type action to bite away at sheet metal. They cut like a pair of scissors making their way through metal at about 1/4 inch per cut.
video of Sheet Metal Shear Cutters Hand Nibblers for Case Mods and Crafts: